Commercially available flat-irons measure the temperature of the soleplate and do not measure the temperature of the fabric itself. This is because it is difficult to measure a fabric temperature without this temperature being influenced to at least some extent by the soleplate temperature. Nevertheless, controlling the fabric temperature during ironing is a parameter which is important in order to obtain a good ironing quality.
The document JP 4-5998 describes a flat-iron comprising in particular a thermal detector for measuring the temperature of a fabric during ironing. The detector is disposed in the soleplate of the iron. In order to ensure that the detector is not influenced too strongly by the temperature of the soleplate of the iron, a thermal shielding is arranged around the detector. The document does not disclose the composition of the thermal shielding.
When a thermal detector which operates by contact with the fabric is placed on the fabric the temperature of the thermal detector should balance with that of the fabric. However, this balance may be disturbed by the high temperature of the soleplate, which gives rise to substantial thermal disturbances.
Moreover, the measurement of the fabric temperature should be carried out while the iron is moved over the fabric. Indeed, the iron cannot remain motionless at the risk of the fabric being burnt. Therefore, in order to control the parameters of the flat-iron, the response times of the detectors should be very small. The detector should therefore have a low thermal inertia without thereby becoming susceptible to thermal contributions of the soleplate. Therefore, the detector temperature should not be influenced too much by the soleplate temperature, both under dynamic and under static conditions.
In addition to these problems, which are related to heat transfer, there are several mechanical problems. First of all, there are problems as to the mechanical properties of the detector, which should be solved without the detector being adversely affected by repeated and considerable bending of the support which supports the detector. Secondly, there are mechanical problems in connection with the size. On the one hand, the detector should be mounted in the soleplate of a few millimeters thickness. On the other hand, the presence of the heating element, the supply of water, steam conduits, etc. does not leave much room to mount the detector and to solve the heat transfer problems.
Therefore, it is difficult to meet all these requirements at the same time, which partly explains why commercially available irons are not equipped with thermal detectors for the fabric.